I used to catch most things by spamming Ultra Balls without focusing much on damage/status unless it was a high level. Legendaries were the main thing that might need repeated reloads - for those not familiar with the games, most legendaries are a one-shot deal; if you fail to catch them and either lose or defeat it, you can't try again without starting a new game, so everyone always saved before attempting to battle them so they could reload on failure. There are a few legendaries that are exceptions, which moved around and could be re-encountered if not caught, but they were in generation 2 and upwards.
In Gen I you could just save before attempting to catch one, so if you did kill it you could just restart from your save point. You couldn't really do this in Gen II for the Legendary Dogs because they showed up randomly, and sometimes you had the horrible decision of; never catch Entei or redo those last 3 hours of cave...
The legendary dogs only moved between areas when you did, so you could wait until you were in the same area as one, save, then have multiple tries at catching it; the main difficulty was in quickly incapacitating it so it wouldn't run away or else capturing it on your first turn without any weakening.
